Electrically driven compressors must convert rotary motion from a motor into linear motion to actuate a piston or a series of pistons to generate compressed gas. Most compressors accomplish this task by means of a crankshaft and connecting rod assembly, similar to that found in internal combustion engines. Some advantages to this design are the proven reliability and the high operating efficiency. One major disadvantage is the space required by the connecting rod throughout the complete cycle. This disadvantage becomes particularly evident in multistage compressors used for compressing gas to high pressures, typically greater than 1000 psig. Often, the pistons and cylinders used in the higher stages of these compressors are not large enough to accommodate the connecting rod and the dynamic space it occupies. As a result, many designs limit the piston travel to under 0.5 inches, and use stepped pistons in the higher pressure stages. These actions reduce the compressor efficiency and add components to the assembly.
Other designs for compressors utilize nutating heads to convert rotary motion into linear motion. In these designs, the piston travel is parallel to the axis of rotation. Automotive air conditioning compressors commonly use this type of compressor. An advantage of this style compressor is the low amount of package space required by the compressor. In addition, the connecting rods, if any are used at all, articulate less than those used with crankshafts. This allows more travel in small diameter pistons than with crankshaft designs. One disadvantage to this style of compressor is the piston reciprocation relies mostly on sliding action than rolling action. This increases the amount of friction in the system, and lowers overall compressor efficiency.
It is a principal object of the present invention to combine the rolling action from crankshaft driven compressors with the high piston travel found in nutating head compressors.